/
PubSubAuthenticatedPush.java
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/
PubSubAuthenticatedPush.java
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/*
* Copyright 2019 Google LLC
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.example.appengine.pubsub;
import com.google.api.client.googleapis.auth.oauth2.GoogleIdToken;
import com.google.api.client.googleapis.auth.oauth2.GoogleIdTokenVerifier;
import com.google.api.client.http.javanet.NetHttpTransport;
import com.google.api.client.json.gson.GsonFactory;
import com.google.gson.Gson;
import com.google.gson.JsonElement;
import com.google.gson.JsonParser;
import java.io.IOException;
import java.util.Base64;
import java.util.Collections;
import java.util.stream.Collectors;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
// [START gae_standard_pubsub_auth_push]
@WebServlet(value = "/pubsub/authenticated-push")
public class PubSubAuthenticatedPush extends HttpServlet {
private final String pubsubVerificationToken = System.getenv("PUBSUB_VERIFICATION_TOKEN");
private final MessageRepository messageRepository;
private final GoogleIdTokenVerifier verifier =
new GoogleIdTokenVerifier.Builder(new NetHttpTransport(), new GsonFactory())
/**
* Please change example.com to match with value you are providing while creating
* subscription as provided in @see <a
* href="https://github.com/GoogleCloudPlatform/java-docs-samples/tree/main/appengine-java8/pubsub">README</a>.
*/
.setAudience(Collections.singletonList("example.com"))
.build();
private final Gson gson = new Gson();
@Override
public void doPost(HttpServletRequest req, HttpServletResponse resp)
throws IOException, ServletException {
// Verify that the request originates from the application.
if (req.getParameter("token").compareTo(pubsubVerificationToken) != 0) {
resp.setStatus(HttpServletResponse.SC_BAD_REQUEST);
return;
}
// Get the Cloud Pub/Sub-generated JWT in the "Authorization" header.
String authorizationHeader = req.getHeader("Authorization");
if (authorizationHeader == null
|| authorizationHeader.isEmpty()
|| authorizationHeader.split(" ").length != 2) {
resp.setStatus(HttpServletResponse.SC_BAD_REQUEST);
return;
}
String authorization = authorizationHeader.split(" ")[1];
try {
// Verify and decode the JWT.
// Note: For high volume push requests, it would save some network overhead
// if you verify the tokens offline by decoding them using Google's Public
// Cert; caching already seen tokens works best when a large volume of
// messsages have prompted a single push server to handle them, in which
// case they would all share the same token for a limited time window.
GoogleIdToken idToken = verifier.verify(authorization);
GoogleIdToken.Payload payload = idToken.getPayload();
// IMPORTANT: you should validate claim details not covered by signature
// and audience verification above, including:
// - Ensure that `payload.getEmail()` is equal to the expected service
// account set up in the push subscription settings.
// - Ensure that `payload.getEmailVerified()` is set to true.
messageRepository.saveToken(authorization);
messageRepository.saveClaim(payload.toPrettyString());
// parse message object from "message" field in the request body json
// decode message data from base64
Message message = getMessage(req);
messageRepository.save(message);
// 200, 201, 204, 102 status codes are interpreted as success by the Pub/Sub system
resp.setStatus(102);
super.doPost(req, resp);
} catch (Exception e) {
resp.setStatus(HttpServletResponse.SC_BAD_REQUEST);
}
}
private Message getMessage(HttpServletRequest request) throws IOException {
String requestBody = request.getReader().lines().collect(Collectors.joining("\n"));
JsonElement jsonRoot = JsonParser.parseString(requestBody).getAsJsonObject();
String messageStr = jsonRoot.getAsJsonObject().get("message").toString();
Message message = gson.fromJson(messageStr, Message.class);
// decode from base64
String decoded = decode(message.getData());
message.setData(decoded);
return message;
}
private String decode(String data) {
return new String(Base64.getDecoder().decode(data));
}
PubSubAuthenticatedPush(MessageRepository messageRepository) {
this.messageRepository = messageRepository;
}
public PubSubAuthenticatedPush() {
this(MessageRepositoryImpl.getInstance());
}
}
// [END gae_standard_pubsub_auth_push]